Background reduction of Compton-camera based 3D imaging for range verification in proton therapy

Low signal-to-background ratio and subsequent image degradation limits the performance of Compton cameras and hinder their application for range verification in hadron therapy. While several approaches have been explored to improve the signal-to-background ratio via event selection (e.g. with neural networks, energy cuts or using dedicated hardware), background reduction within the 3D image reconstruction process has been hitherto overlooked. In this work we present three such background reduction techniques, and show their potential for image-quality improvement by using simulated data. The explored techniques are shown to reduce image noise-edge artifacts, as well as improve the image contrast and/or be quantitatively closer to the ground truth spatial emission distribution. Such promising results encourage further study on their implementation and impact on range verification.